Electronic digital devices typically emit a spectrum of light, consisting of rays of varying wavelengths, of which the human eye is able to detect a visible spectrum between about 350 to about 700 nanometers (nm). It has been appreciated that certain characteristics of this light, both in the visible and nonvisible ranges, may be harmful to the user, and lead to health symptoms and adverse health reactions, such as, but not limited to, eyestrain, dry and irritated eyes, fatigue, blurry vision and headaches. There may be a link between exposure to the blue light found in electronic devices and human health hazards, particularly with potentially harmful risks for the eye. Some believe that exposure to the blue light and/or high energy visible light, such as that emitted by screens of digital devices could lead to age-related macular degeneration, decreased melatonin levels, acute retinal injury, accelerated aging of the retina, and disruption of cardiac rhythms, among other issues. Additional research may reveal additional musculoskeletal issues that result from prolonged exposure to the blue light spectrum.
More specifically, high energy visible (HEV) light emitted by digital devices is known to increase eye strain more than other wavelengths in the visible light spectrum. Blue light can reach deeper into the eye than, for example, ultraviolet light and may cause damage to the retina. Additionally, there may also be a causal link between blue light exposure and the development of Age-related Macular Degeneration (AMD) and cataracts. Additionally, the use of digital electronic devices is known to cause eye strain symptoms. The damage is thought to be caused by HEV light that penetrates the macular pigment, causing more rapid retinal changes.
Additionally, blue light exposure suppresses melatonin for about twice as long as green light and shifts circadian rhythms by twice as much. Blue wavelengths of light seem to be the most disruptive at night. Studies have also shown that blue light frequencies, similar to those generated by LEDs from electronic devices, such as smart phones, are 50 to 80 times more efficient in causing photoreceptor death than green light. Exposure to the blue light spectrum seem to accelerate AMD more than other areas of the visible light spectrum. However, it is also suspected that exposure to the red and green light spectrums may also present health risks, which can be mitigated by absorption of light produced by devices in that wavelength range.
Further, ultraviolet A (UVA) light (in the 320-380 nm range) is of particular concern to eye care professionals. UVA light is considered to be damaging because it directly affects the crystalline lens of the human eye. In one embodiment, the film 200 reduces the High Energy Visible light in accordance with the standards set by the International Safety Equipment Association, specifically the ANSI/ISEA Z87.1-2010 standard, which weighs the spectral sensitivity of the eye against the spectral emittance from the 380-1400 nm range.
Although the light generated by LEDs from digital devices appears normal to human vision, a strong peak of blue light ranging from 380-500 nanometers is also emitted within the white light spectrum produced by the screens of such digital devices. As this blue light corresponds to a known spectrum for retinal hazards, a means for protecting users from exposure to such light is needed.
Optical filters are used in a wide range of applications including light filters for LCD (Liquid Crystal Display) retardation films. LCD retardation films use alternate layers of materials comprised of an electroplated pigment, pigment impregnated or a printing method materials. These methods are compromised when they experience friction, heat or moisture and may cause a ghosting effect. Optical density transmissivity and sustainability requirements may also fail due to moisture and mechanical integrity.
While some measures have been taken to reduce exposure to these harmful rays, these measure have been inadequate. Some measures have implemented software solutions to decrease the wavelengths emitted, but they are easily altered to be less effective and can change the viewing experience by blocking too much light from a chosen wavelength and, therefore, changing the colors viewable to a user. Other measures have implemented physical devices that are placed over screens. However, these devices severely alter the colors viewable to a user and, in most cases, completely block at least one entire color from the color spectrum.
More specifically, current film substrate technologies often lack desired optical properties such as stability to UV light, selective transmissivity in the visible range, and absorption in the UV and high intensity blue light range, or other absorption characteristics. Current film substrates also lack the desired mechanical properties such as heat resistance and mechanical robustness at the desired thinness. Glass, polycarbonate, acrylic, and nylon lenses and films exist, but may be unable to sustain dye or pigment dispersion and achieve an optical density sufficient to maintain the high transmission values at this thickness. In one embodiment, an F700 film, such as that produced by Kentek Corporation, is resistant to moisture and humidity. Such a film is preferable to glass, which may require re-polishing. Increased color resolution, repeatability and the lack of a binder agent requirement are other benefits.